1. Field of the Invention
This invention relates generally to antennas, and more specifically to the structure and assembly of a patch antenna utilizing a polymer plastic dielectric layer providing a reasonable sized antenna at a substantially reduced cost.
2. Description of the Prior Art
A conventional patch antenna in its simplest form is made of a rectangular conductive radiating element overlapping and approximately parallel with a conductive ground plate. A dielectric layer, or element, separates the radiating element from the ground plate. A basic structure of a typical patch antenna is shown in FIG. 1. The patch antenna 10 is assembled with the dielectric layer 15 sandwiched between the radiating element 12 and the ground plate 17.
As is well known in the art, many of the properties of a patch antenna, specifically including size and cost, depend to a great degree upon the composition of the dielectric layer. Besides the cost of the dielectric layer itself, the dielectric constant of the dielectric layer directly affects the dimensions of the distributed circuit components. At one extreme, air can be considered the dielectric layer. Air is obviously quite inexpensive, however air's low dielectric constant of 1.0 requires a relatively large-sized radiating element, which is not desirable in today's world of increasing miniaturization. Near the opposite extreme of commonly used dielectric layers, ceramic's dielectric constant of 7.0–10.0 permits a relatively small-sized radiating element, with a downside of a markedly increased cost.
Wide varieties of other materials are available for use as a dielectric layer. Some other common dielectric layer examples include foam and high frequency printed circuit boards (PCB). The use of a PCB as the dielectric layer permits a relatively small sized antenna, but is quite expensive. Foam is quite inexpensive, but requires a much larger antenna due to its low dielectric constant. Additionally, extreme changes in temperature make some materials unacceptable because temperature changes may break or alter bonding between the relative components or damage the assembled antenna. Thus, manufacture, assembly, and reliability considerations frequently far outweigh any potential saving achieved by the choice of an inexpensive material having a relatively high dielectric constant.